Has anyone been able to get the instant hotspot to work consistently between ios 8 and yosemite? It seems to work maybe 10% of the time for me, usually I end up having to plug my phone into my Macbook Air to get the tethering to actually work.
Nope, I've been frustrated with the same issue with my mid-2014 macbook pro. Like you, it works occassionally but manually tethering always works. Seems like a broken feature.